The noticeable content of benefit agents, particularly perfumes or flavors, significantly influence the consumers' decision whether to buy a personal care composition or not. The noticeable content of perfumes or flavors, herein collectively designated as fragrance, is of most importance at two places. First, the headspace concentration of the fragrance, that means the concentration in the volume left at the top of a container filled with the personal care composition, is of high importance. The fragrance concentration in the headspace is directly noticeable by the consumer before and during the use of the personal care composition. Second, the fragrance that is left on the substrate after the use of the composition, for example on hair or skin, is of high importance to consumers. In the second case, the amount of other benefit agents that are left after the use of the composition on the substrate is also important. Among others the deposition of a sunscreen agent, a moisturizing agent, or an emollient on hair or skin is of high importance. These factors significantly influence the consumers' decision whether to buy the composition or not. Much research effort has been spent on increasing the noticeable fragrance content in consumer products without undue increase of costs.
U.S. Pat. No. 6,172,037 discloses a perfume fixative for enhancing the perfume life. The perfume fixative consists essentially of polyvinylpyrrolidone, hydroxypropyl cellulose and hydrophobic oil. The polyvinylpyrrolidone and hydroxypropyl cellulose together should not constitute more than about 0.5 percent, by weight of the perfume-containing product. The perfume fixative is intended for perfumed leave-on skin products, particularly ethanol-based (deo)colognes, personal perfumes, antiperspirant deodorants and hair colognes.
The published U.S. Patent Application No. 2004/0087476 discloses a benefit agent delivery system for delivering a benefit agent to a substrate. The benefit agent delivery system comprises polymer particles and a benefit agent, such as a perfume. The polymer particles are water-insoluble and have an average particle size of from 100 nm to 50 micrometers. Disclosed polymer particles are polystyrene and poly(methyl methacrylate-dimethyl amino ethyl methacrylate) copolymer. The Patent Application discloses the importance of adding the polymer particles and the benefit agent separately to a matrix to form the benefit agent delivery system.
Many personal care compositions comprise low molecular weight surfactants for cleansing purposes, as a foaming agent, for increasing the viscosity of the composition or a combination thereof. An increased viscosity is desired for many applications to facilitate the handling of the composition and to extend the contact time between the composition and the substrate to which the composition is applied, such as skin or hair.
One object of the present invention is to find a method of improving the deposition of a benefit agent on a substrate after treatment of the substrate with a water-based personal care composition.
Another object of the present invention is to find a method of increasing the headspace concentration of a fragrance provided by a water-based personal care composition.
It has surprisingly been found that these objects can be achieved in a simple manner in water-based personal care compositions which have a viscosity of at least 50 mPa·s at 25° C. and comprise the benefit agent and a low molecular weight surfactant if at least a portion of the low molecular weight surfactant is replaced by a water-soluble polymer.